U.S. patent number 10,041,224 [Application Number 15/113,926] was granted by the patent office on 2018-08-07 for liquid-pressure driving system.
This patent grant is currently assigned to KAWASAKI JUKOGYO KABUSHIKI KAISHA. The grantee listed for this patent is KAWASAKI JUKOGYO KABUSHIKI KAISHA. Invention is credited to Kazuto Fujiyama, Makoto Ito, Akihiro Kondo.
United States Patent |
10,041,224 |
Kondo , et al. |
August 7, 2018 |
Liquid-pressure driving system
Abstract
A hydraulic driving system includes first to third
liquid-pressure pumps and control valves. The first boom control
valve is connected to the first hydraulic pump, and the second arm
control valve and the first bucket control valve are connected to
the second liquid-pressure pump. Further, the turning control valve
and the second bucket control valve are connected to the third
hydraulic pump. When a pilot pressure XAk0 is output from a bucket
operating device while a turning operation is performed, a command
switching device outputs a pilot pressure XAk1 to the first bucket
control valve. When the pilot pressure XAk0 is output from the
bucket operating device while the turning operation is performed,
the command switching device outputs a pilot pressure XAk2 to a
second bucket control valve.
Inventors: |
Kondo; Akihiro (Nishinomiya,
JP), Ito; Makoto (Kobe, JP), Fujiyama;
Kazuto (Kobe, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
KAWASAKI JUKOGYO KABUSHIKI KAISHA |
Kobe-shi, Hyogo |
N/A |
JP |
|
|
Assignee: |
KAWASAKI JUKOGYO KABUSHIKI
KAISHA (Kobe-shi, JP)
|
Family
ID: |
53681204 |
Appl.
No.: |
15/113,926 |
Filed: |
January 14, 2015 |
PCT
Filed: |
January 14, 2015 |
PCT No.: |
PCT/JP2015/000144 |
371(c)(1),(2),(4) Date: |
July 25, 2016 |
PCT
Pub. No.: |
WO2015/111390 |
PCT
Pub. Date: |
July 30, 2015 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20160348335 A1 |
Dec 1, 2016 |
|
Foreign Application Priority Data
|
|
|
|
|
Jan 23, 2014 [JP] |
|
|
2014-010409 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E02F
3/422 (20130101); E02F 9/2225 (20130101); E02F
9/2242 (20130101); F15B 13/06 (20130101); E02F
9/2285 (20130101); E02F 9/2296 (20130101); E02F
9/2004 (20130101); E02F 9/2292 (20130101); E02F
9/2228 (20130101); F15B 11/17 (20130101); E02F
9/2282 (20130101); F15B 2211/329 (20130101); F15B
2211/7142 (20130101); F15B 2211/6316 (20130101); F15B
2211/20576 (20130101); F15B 2211/30595 (20130101); F15B
2211/45 (20130101); F15B 2211/20546 (20130101); F15B
2211/255 (20130101); F15B 2211/355 (20130101); F15B
2211/7058 (20130101); F15B 2211/71 (20130101); E02F
9/2232 (20130101); F15B 2211/6355 (20130101); F15B
2211/20553 (20130101); F15B 2211/7135 (20130101) |
Current International
Class: |
E02F
9/22 (20060101); E02F 9/20 (20060101); E02F
3/42 (20060101); F15B 11/17 (20060101); F15B
13/06 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
2009-002441 |
|
Jan 2009 |
|
JP |
|
2009-293021 |
|
Dec 2009 |
|
JP |
|
2012-021311 |
|
Feb 2012 |
|
JP |
|
2013-148175 |
|
Aug 2013 |
|
JP |
|
Other References
Apr. 21, 2015 International Search Report issued in International
Patent Application No. PCT/JP2015/000144. cited by applicant .
Aug. 4, 2016 International Preliminary Report on Patentability
issued in International Patent Application No. PCT/JP2015/000144.
cited by applicant .
Apr. 12, 2017 Office Action issued in Chinese Patent Application
No. 201380027881.X. cited by applicant.
|
Primary Examiner: Lazo; Thomas E
Attorney, Agent or Firm: Oliff PLC
Claims
The invention claimed is:
1. A liquid-pressure driving system comprising: first and second
liquid-pressure pump each configured to supply a pressure liquid to
a boom actuator through at least one boom control valve, to an arm
actuator through at least one arm control valve, and to a bucket
actuator through a first bucket control valve; a third
liquid-pressure pump configured to supply the pressure liquid to
the bucket actuator through a second bucket control valve and to a
turning motor through a turning control valve; and a command output
device configured to when supplying the pressure liquid to the
bucket actuator while the pressure liquid is supplied from the
third liquid-pressure pump to the turning motor, output a first
bucket drive command to the first bucket control valve such that
the pressure liquid is supplied from the first or second
liquid-pressure pump through the first bucket control valve to the
bucket actuator and when supplying the pressure liquid to the
bucket actuator while the pressure liquid is not supplied to the
turning motor, output a second bucket drive command such that the
pressure liquid is supplied from the third liquid-pressure pump
through the second bucket control valve to the bucket actuator.
2. The liquid-pressure driving system according to claim 1, further
comprising a bucket operating device including an operating lever
and configured to output a bucket drive command in accordance with
an operation amount of the operating lever, wherein: the first to
third liquid-pressure pumps are configured such that ejection
amounts thereof are substantially the same as one another; the
command output device outputs the first bucket drive command or the
second bucket drive command in accordance with the bucket drive
command; the first bucket control valve connects the first and
second pressure liquid pumps and the bucket actuator by an opening
area corresponding to the first bucket drive command from the
command output device; the second bucket control valve connects the
third pressure liquid pump and the bucket actuator by an opening
area corresponding to the second bucket drive command from the
command output device; and the opening area of the first bucket
control valve and the opening area of the second bucket control
valve are substantially the same as each other when the first
bucket drive command and the second drive command are substantially
the same as each other.
3. The liquid-pressure driving system according to claim 1,
wherein: the arm control valve is connected to at least one of the
first liquid-pressure pump and the second liquid-pressure pump; and
the boom control valve is connected to the other liquid-pressure
pump.
4. The liquid-pressure driving system according to claim 1,
wherein: the at least one arm control valve comprises two arm
control valves, and the two arm control valves are connected to the
first liquid-pressure pump and the second liquid-pressure pump,
respectively; the at least one boom control valve comprises two
boom control valves, and the two boom control valves are connected
to the first liquid-pressure pump and the second liquid-pressure
pump, respectively; when lowering a boom that is lifted or lowered
by the boom actuator, one of the two boom control valves stops
supply of the pressure liquid to the boom actuator from the
liquid-pressure pump to which the one boom control valve is
connected; and the first bucket control valve is connected to the
liquid-pressure pump to which the one boom control valve is
connected.
5. The liquid-pressure driving system according to claim 1,
wherein: the first to third liquid-pressure pumps are variable
displacement pumps; the first to third liquid-pressure pumps are
provided with first to third regulators, respectively, the first to
third regulators being configured to control ejection amounts of
the first to third liquid-pressure pumps, respectively; and the
third regulator controls the ejection amount of the third
liquid-pressure pump separately from the ejection amounts of the
first and second liquid-pressure pumps.
6. The liquid-pressure driving system according to claim 1,
wherein: the first bucket control valve includes a first bucket
spool configured to move to a position corresponding to the first
bucket drive command and connect the first and/or second
liquid-pressure pump and the bucket actuator by an opening area
corresponding to an amount of movement of the first bucket spool
and a movement regulating mechanism configured to regulate the
amount of movement of the first bucket spool; and when the pressure
liquid is supplied to at least one of the boom actuator and the arm
actuator while the pressure liquid is supplied to the turning
motor, and the command output device outputs the first bucket drive
command, the movement regulating mechanism regulates the amount of
movement of the first bucket spool.
7. The liquid-pressure driving system according to claim 1,
wherein: the command output device includes an electromagnetic
control valve configured to adjust a pilot pressure output as the
first bucket drive command to the first bucket control valve and a
control unit configured to control an operation of the
electromagnetic control valve; the first bucket control valve
connects the third liquid-pressure pump and the bucket actuator by
an opening area corresponding to the pilot pressure, and the
opening area of the first bucket control valve decreases when the
pilot pressure is reduced; and when the pressure liquid is supplied
to at least one of the boom actuator and the arm actuator while the
pressure liquid is supplied to the turning motor, and the command
output device outputs the first bucket drive command, the control
unit reduces the pilot pressure by the electromagnetic control
valve.
Description
TECHNICAL FIELD
The present invention relates to a liquid-pressure driving system
configured to drive a turning motor, an arm actuator, a boom
actuator, and a bucket actuator.
BACKGROUND ART
A construction machine such as a hydraulic excavator includes a
hydraulic driving system and a plurality of actuators and drives
the actuators by introducing pressure oil from the hydraulic
driving system to the actuators. Known as the hydraulic driving
system of the construction machine configured as above is, for
example, a hydraulic driving device of PTL 1.
The hydraulic driving device of PTL 1 includes three pumps. By
introducing operating oil from these three pumps to various
actuators such as a traveling motor, a turning motor, a boom
actuator, an arm actuator, and a bucket actuator, the hydraulic
driving device can perform traveling, turning, lifting and lowering
of a boom, bending and extending of an arm, and excavating and
dumping of a bucket. Those actuators are provided with
corresponding control valves, and each of the control valves
changes a state of supplying the operating oil to the corresponding
actuator. Those control valves constitute three control valve
groups, and a first control valve group is connected to a first
pump. A second control valve group and a third control valve group
are connected to a second pump and a third pump, respectively.
The first control valve group includes a turning control valve, a
boom control valve, an arm control valve, and a bucket control
valve. The second control valve group includes an arm control
valve, a boom control valve, and a bucket control valve. The third
control valve group includes an arm control valve. By operating
lever devices correspondingly provided at the control valves of the
second and third control valve groups, pilot pressure is input to
the control valves of the second and third control valve groups.
The control valves of the second and third control valve groups
operate by the pilot pressure to supply the operating oil, ejected
from the second and third pumps, to the corresponding actuators.
Further, by operating the lever devices correspondingly provided at
the control valves of the first control valve group other than the
turning control valve, pilot pressure regulated by an
electromagnetic control valve is input to the control valves of the
first control valve group other than the turning control valve.
When the turning control valve operates, the pilot pressure input
to the control valves of the first control valve group other than
the turning control valve is blocked. Thus, when the boom, the arm,
or the bucket is operated at the same time as the turning
operation, the operating oil ejected from the third pump can be
supplied only to the turning motor.
CITATION LIST
Patent Literature
PTL 1: Japanese Laid-Open Patent Application Publication No.
2012-21311
SUMMARY OF INVENTION
Technical Problem
In the hydraulic driving device of PTL 1, the control valves of the
first control valve group other than the turning control valve are
utilized as control valves that assist the control valves of the
second and third control valve groups. To be specific, when the
amount of operating oil supplied from the control valves of the
second and third control valve groups to the corresponding
actuators is inadequate, the control valves of the first control
valve group other than the turning control valve supply the
operating oil to those actuators. Further, the pilot pressure input
to the control valves of the first control valve group other than
the turning control valve is blocked at the time of the turning
operation. Therefore, when the boom, the arm, or the bucket is
operated at the same time as the turning operation, the operating
oil cannot be supplied to each actuator, such as the boom, the arm,
or the bucket, at a required flow rate.
An object of the present invention is to provide a liquid-pressure
driving system capable of introducing operating oil to each
actuator such as a boom, an arm, or a bucket at a required flow
rate even when the actuator is operated at the same time as a
turning operation.
Solution to Problem
A liquid-pressure driving system of the present invention includes:
first and second liquid-pressure pump each configured to supply a
pressure liquid to a boom actuator through a boom control valve, to
an arm actuator through an arm control valve, and to a bucket
actuator through a first bucket control valve; a third
liquid-pressure pump configured to supply the pressure liquid to
the bucket actuator through a second bucket control valve and to a
turning motor through a turning control valve; and a command output
device configured to when operating the bucket actuator while the
pressure liquid is supplied from the third liquid-pressure pump to
the turning motor, output a first bucket drive command to the first
bucket control valve such that the pressure liquid is supplied from
the first or second liquid-pressure pump through the first bucket
control valve to the bucket actuator and when operating the bucket
actuator while the pressure liquid is not supplied to the turning
motor, output a second bucket drive command such that the pressure
liquid is supplied from the third liquid-pressure pump through the
second bucket control valve to the bucket actuator.
According to the present invention, the pressure liquid is not
supplied to the boom actuator and the arm actuator from the third
liquid-pressure pump configured to supply the pressure liquid to
the turning motor. Therefore, regardless of whether or not the
pressure liquid is supplied to the turning motor, the pressure
liquid can be supplied from the first or second liquid-pressure
pump to the boom actuator or the arm actuator at a required flow
rate. Further, the pressure liquid can be supplied to the bucket
actuator from not only the third liquid-pressure pump but also the
first or second liquid-pressure pump through the first bucket
control valve, and the first to third liquid-pressure pumps are
selectively used in accordance with whether or not the pressure
liquid is supplied to the turning motor. Therefore, the pressure
liquid can be introduced from the first to third liquid-pressure
pumps to the bucket actuator at a required flow rate regardless of
whether or not the turning operation is performed.
As above, according to the present invention, the pressure liquid
can be supplied to each of the boom actuator, the arm actuator, and
the bucket actuator at a required flow rate regardless of whether
or not the pressure liquid is supplied to the turning motor.
Therefore, even when the boom, the arm, or the bucket is operated
at the same time as the turning operation, the pressure liquid can
be introduced to each actuator at a required flow rate.
In the above invention, the liquid-pressure driving system may
further include a bucket operating device including an operating
lever and configured to output a bucket drive command in accordance
with an operation amount of the operating lever, wherein: the first
to third liquid-pressure pumps may be configured such that ejection
amounts thereof are substantially the same as one another; the
bucket operating device includes the operating lever that is
operable and outputs the bucket drive command in accordance with
the operation amount of the operating lever; the command output
device may output the first bucket drive command or the second
bucket drive command in accordance with the bucket drive command;
and the first bucket control valve may connect the first to third
pressure liquid pumps and the bucket actuator by an opening area
corresponding to the first bucket drive command from the command
output device, and the second bucket control valve may connect the
first to third pressure liquid pumps and the bucket actuator by an
operating area corresponding to the second bucket drive command
from the command output device, the opening area of the first
bucket control valve and the opening area of the second bucket
control valve being substantially the same as each other when the
first bucket drive command and the second drive command are
substantially the same as each other.
According to the above configuration, when the first bucket drive
command and the second bucket drive command are substantially the
same as each other, the extension/contraction speed of the bucket
actuator based on the first bucket drive command and the
extension/contraction speed of the bucket actuator based on the
second bucket drive command can be made substantially the same as
each other. With this, regardless of whether or not the turning
operation is performed at the same time, the bucket can be operated
by the substantially same operational feeling.
In the above invention, the liquid-pressure driving system may be
configured such that: the arm control valve is connected to at
least one of the first liquid-pressure pump and the second
liquid-pressure pump; and the boom control valve is connected to
the other liquid-pressure pump.
According to the above configuration, when supplying the pressure
liquid to the arm actuator and the boom actuator at the same time,
the pressure liquid can be supplied to those actuators from
different liquid-pressure pumps through the corresponding control
valves. Therefore, even when the arm operating device and the boom
operating device are operated at the same time, the lack of the
flow rate of the pressure liquid introduced to each actuator can be
suppressed.
In the above invention, the liquid-pressure driving system may be
configured such that: the arm control valve includes two arm
control valves, and the two arm control valves are connected to the
first liquid-pressure pump and the second liquid-pressure pump,
respectively; the boom control valve includes two boom control
valves, and the two boom control valves are connected to the first
liquid-pressure pump and the second liquid-pressure pump,
respectively; when lowering a boom, one of the two boom control
valves stops supply of the pressure liquid to the bucket actuator
from the liquid-pressure pump to which the one boom control valve
is connected; and the first bucket control valve is connected to
the liquid-pressure pump to which the one boom control valve is
connected.
According to the above configuration, when lowering the boom, the
pressure liquid of one of the liquid-pressure pumps is not supplied
to the boom actuator. Therefore, even when the boom is lowered and
the bucket is driven while the pressure liquid is supplied to the
turning motor, the pressure liquid can be supplied to the bucket
actuator at a required flow rate.
In the above invention, the liquid-pressure driving system may be
configured such that: the first to third liquid-pressure pumps are
variable displacement pumps; the first to third liquid-pressure
pumps are provided with first to third regulators, respectively,
the first to third regulators being configured to control ejection
amounts of the first to third liquid-pressure pumps, respectively;
and the third regulator controls the ejection amount of the third
liquid-pressure pump separately from the ejection amounts of the
first and second liquid-pressure pumps.
According to the above configuration, when supplying the pressure
liquid to the turning motor, the third liquid-pressure pump can
eject the pressure liquid at a flow rate required for the turning
motor. Thus, energy saving of the liquid-pressure driving system
can be achieved.
In the above invention, the liquid-pressure driving system may be
configured such that: the first bucket control valve includes a
first bucket spool configured to move to a position corresponding
to the first bucket drive command and connect the liquid-pressure
pump and the bucket actuator by an opening area corresponding to an
amount of movement of the first bucket spool and a movement
regulating mechanism configured to regulate the amount of movement
of the first bucket spool; and when the pressure liquid is supplied
to at least one of the boom actuator and the arm actuator while the
pressure liquid is supplied to the turning motor, and the command
output device outputs the first bucket drive command, the movement
regulating mechanism regulates the amount of movement of the first
bucket spool,
According to the above configuration, when supplying the pressure
liquid to the bucket and one of the arm actuator and the boom
actuator at the same time while the pressure liquid is supplied to
the turning motor, the amount of movement of the bucket spool of
the bucket control valve can be regulated. With this, the pressure
liquid can be prevented from being introduced at an excessive flow
rate to the bucket actuator whose load is low. Thus, the bucket
whose load is low and the arm or boom whose load is high can be
operated at the same time.
In the above invention, the liquid-pressure driving system may be
configured such that: the command output device includes an
electromagnetic control valve configured to adjust a pilot pressure
output as the first bucket drive command to the first bucket
control valve and a control unit configured to control an operation
of the electromagnetic control valve; the first bucket control
valve connects the liquid-pressure pump and the bucket actuator by
an opening area corresponding to the pilot pressure, and the
opening area of the first bucket control valve decreases when the
pilot pressure is reduced; and when the pressure liquid is supplied
to at least one of the boom actuator and the arm actuator while the
pressure liquid is supplied to the turning motor, and the command
output device outputs the first bucket drive command, the control
unit reduces the pilot pressure by the electromagnetic control
valve.
According to the above configuration, when supplying the pressure
liquid to the bucket and one of the arm actuator and the boom
actuator at the same time while the pressure liquid is supplied to
the turning motor, the amount of movement of the bucket spool of
the bucket control valve can be regulated. With this, the pressure
liquid can be prevented from being introduced at an excessive flow
rate to the bucket actuator whose load is low. Thus, the bucket
whose load is low and the arm or boom whose load is high can be
operated at the same time.
Advantageous Effects of Invention
According to the present invention, even when a boom, an arm, or a
bucket is operated at the same time as a turning operation,
pressure liquid can be introduced to each actuator at a required
flow rate.
The above object, other objects, features, and advantages of the
present invention will be made clear by the following detailed
explanation of preferred embodiments with reference to the attached
drawings.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a circuit diagram showing a hydraulic circuit of a
driving system of a hydraulic driving system according to
Embodiment 1 of the present invention.
FIG. 2 is a circuit diagram show in a hydraulic circuit of an
operating system of the hydraulic driving system of FIG. 1.
FIG. 3 is a circuit diagram showing the hydraulic circuit of the
operating system of the hydraulic driving system according to
Embodiment 2 of the present invention.
FIG. 4 is a circuit diagram showing the hydraulic circuit of the
operating system of the hydraulic driving system according to
Embodiment 3 of the present invention.
DESCRIPTION OF EMBODIMENTS
Hereinafter, hydraulic driving systems 1, 1A, and 1B according to
Embodiments 1 to 3 of the present invention will be explained in
reference to the drawings. It should be noted that a concept of
directions mentioned in the following explanations is used for
convenience of explanation, and this concept does not limit the
directions and the like of components of the present invention.
Further, each of the hydraulic driving systems 1, 1A, and 1B
explained below is just one embodiment of the present invention.
Therefore, the present invention is not limited to those
embodiments, and additions, deletions, and modifications may be
made within the scope of the present invention.
A construction machine such as a hydraulic excavator includes a
turning body (not shown) attached to a traveling device or a base
body so as to be turnable. A boom is attached to the turning body.
The boom is configured to be swingable in an upward/downward
direction (i.e., to be able to be lifted and lowered) relative to
the turning body. An arm is attached to a tip end portion of the
boom. The arm is configured to be swingable in the upward/downward
direction (i.e., to be able to be bent and extended) relative to
the boom. Further, a bucket is attached to a tip end portion of the
arm. The bucket is configured to be swingable in a forward/rearward
direction (i.e., to be able to perform excavating and dumping). The
construction machine configured as above includes a turning motor
2, a boom actuator 3, an arm actuator 4, and a bucket actuator 5
for operating the turning body, the boom, the arm, and the bucket.
The turning motor 2 is constituted by a hydraulic motor, and the
actuators 3 to 5 are constituted by hydraulic cylinders. To be
specific, the turning motor 2 and the actuators 3 to 5 are driven
by operating oil, and the construction machine includes a hydraulic
driving system 1 for driving the turning motor 2 and the actuators
3 to 5.
Embodiment 1
The hydraulic driving system 1 according to Embodiment 1 includes
three hydraulic pumps 11 to 13. These three hydraulic pumps 11 to
13 are constituted by, for example, variable displacement swash
plate pumps. Each of the hydraulic pumps 11 to 13 can change an
ejection flow rate of the operating oil by changing a tilt angle of
a corresponding swash plate 11a, 12a, or 13a. The three hydraulic
pumps 11 to 13 are hydraulic pumps (same hydraulic pumps) that are
substantially the same in functions as one another (for example,
maximum and minimum ejection amounts are substantially the same
among the hydraulic pumps 11 to 13, and the ejection amounts
relative to the tilt angles of the swash plates 11a to 13a are
substantially the same among the hydraulic pumps 11 to 13). A first
boom control valve 21 and a first arm control valve 22 are
connected in parallel to a first hydraulic pump 11 that is one of
the hydraulic pumps 11 to 13. The operating oil ejected from the
first hydraulic pump 11 is introduced to the first boom control
valve 21 and the first arm control valve 22.
The first boom control valve 21 includes a spool 21a and is
connected to the boom actuator 3. The first arm control valve 22
includes a spool 22a and is connected to the arm actuator 4. By
moving the spool 21a, the first boom control valve 21 connects the
first hydraulic pump 11 and the actuator 3 to allow the flow of the
operating oil to the actuator 3. The first boom control valve 21
changes the direction of the operating oil flowing to the actuator
3 depending on the position of the spool 21a. Similarly, by moving
the spool 22a, the first arm control valve 22 connects the first
hydraulic pump 11 and the actuator 4 to allow the flow of the
operating oil to the actuator 4. The first arm control valve 22
changes the direction of the operating oil flowing to the actuator
4 depending on the position of the spool 22a. By moving the spools
21a and 22a, the control valves 21 and 22 configured as above can
extend or contact the actuators 3 and 4 (i.e., can lift or lower
the boom and extend or bend the arm). By returning the spools 21a
and 22a to neutral positions, the control valves 21 and 22
configured as above can block the communication between the first
hydraulic pump 11 and the actuator 3 and the communication between
the first hydraulic pump 11 and the actuator 4 to stop the
operations of the actuators 3 and 4.
Although not shown in FIG. 1, in the hydraulic driving system 1, a
variable restrictor is interposed between the first hydraulic pump
11 and the first arm control valve 22. When operating the boom
actuator 3, the variable restrictor restricts the operating oil
flowing from the first hydraulic pump 11 to the first arm control
valve 22, and therefore, the operating oil from the first hydraulic
pump 11 is introduced preferentially to the first boom control
valve 21.
The first hydraulic pump 11 is connected to a first center bleed
line 23. The operating oil ejected from the first hydraulic pump 11
is discharged to a tank 24 through the first center bleed line 23
(bleed-off). The first boom control valve 21 and the first arm
control valve 22 are disposed on the first center bleed line 23 in
this order from an upstream side. An opening area of the first
center bleed line 23 changes depending on the positions of the
spools 21a and 22a. The opening area is the largest when the spools
21a and 22a are located at the neutral positions, and the opening
area decreases in accordance with the amounts of movements of the
spools 21a and 22a from the neutral positions. Therefore, when the
spools 21a and 22a are moved, the opening area of the first center
bleed line 23 is adjusted, and this adjusts the flow rate of the
operating oil that is discharged to the tank 24 through the first
center bleed line 23.
A first restrictor 25 is disposed on the first center bleed line 23
so as to be located between the first arm control valve 22 and the
tank 24. A first relief valve 26 is connected to the first center
bleed line 23 so as to avoid the first restrictor 25. In the first
center bleed line 23, hydraulic pressure at an upstream of the
first restrictor 25 increases or decreases by the first restrictor
25 in accordance with the flow rate of the oil flowing to the first
restrictor 25. When the hydraulic pressure at the upstream of the
first restrictor 25 exceeds predetermined pressure, the operating
oil in the first center bleed line 23 is relieved to the tank 24 by
the first relief valve 26. The hydraulic pressure increased or
decreased by the first restrictor 25 is input as a first negative
control pressure Pn1 to a first regulator 27.
The first regulator 27 adjusts the tilt angle of the swash plate
11a of the first hydraulic pump 11 in accordance with hydraulic
signals input to the first regulator 27. The first negative control
pressure Pn1 and a first ejection pressure Pd1 of the first
hydraulic pump 11 are input as the hydraulic signals to the first
regulator 27. When the first negative control pressure Pn1 or the
first ejection pressure Pd1 increases, the first regulator 27
decreases the tilt angle of the swash plate 11a to reduce the
ejection flow rate of the first hydraulic pump 11. In contrast,
when the first negative control pressure Pn1 or the first ejection
pressure Pd1 decreases, the first regulator 27 increases the tilt
angle of the swash plate 11a to increase the ejection flow rate of
the first hydraulic pump 11. Further, a first power shift pressure
Ps1 is input from a first horsepower controller 28 to the first
regulator 27 configured as above.
The first horsepower controller 28 includes a first electromagnetic
proportional valve 29. Pilot oil is introduced from a
below-described pilot pump 30 to the first horsepower controller
28. The first electromagnetic proportional valve 29 reduces the
pressure of the pilot oil to the first power shift pressure Ps1
corresponding to a first horsepower control signal input to the
first electromagnetic proportional valve 29. The first
electromagnetic proportional valve 29 outputs the first power shift
pressure Ps1 as the hydraulic signal to the first regulator 27. As
with the control with respect to the first negative control
pressure Pn1 and the first ejection pressure Pd1, the first
regulator 27 adjusts the tilt angle of the swash plate 11a in
accordance with the first power shift pressure Ps to control the
ejection flow rate of the first hydraulic pump 11. By inputting the
first power shift pressure Ps1 as above, output horsepower of the
first hydraulic pump 11 can be reduced. In addition to the first
hydraulic pump 11, the first power shift pressure Ps1 is also
introduced to a second regulator 31 for a second hydraulic pump
12.
The second regulator 31 is attached to the second hydraulic pump 12
that is one of the remaining two hydraulic pumps 12 and 13. As with
the first regulator 27, the second regulator 31 adjusts the tilt
angle of the swash plate 12a of the second hydraulic pump 12 in
accordance with the first power shift pressure Ps1, a
below-described second negative control pressure Pn2, and a
below-described second ejection pressure Pd2, which are input as
the hydraulic signals, to control the ejection flow rate of the
second hydraulic pump 12. A first bucket control valve 32, a second
boom control valve 33, and a second arm control valve 34 are
connected to the second hydraulic pump 12 in parallel.
The first bucket control valve 32 includes a spool 32a and is
connected to the bucket actuator 5. By moving the spool 32a, the
first bucket control valve 32 connects the second hydraulic pump 12
and the bucket actuator 5 to allow the flow of the operating oil to
the bucket actuator 5. The first bucket control valve 32 changes
the direction of the operating oil flowing to the bucket actuator 5
depending on the position of the spool 32a. By moving the spool
32a, the first bucket control valve 32 configured as above can
extend or contract the bucket actuator 5 (i.e., can cause the
bucket to perform dumping or excavating). By returning the spool
32a to the neutral position, the first bucket control valve 32
configured as above can block the communication between the second
hydraulic pump 12 and the bucket actuator 5 to stop the operation
of the bucket actuator 5.
The second boom control valve 33 includes a spool 33a and is
connected to the boom actuator 3. By moving the spool 33a, the
second boom control valve 33 can connect the second hydraulic pump
12 and the boom actuator 3 to allow the flow of the operating oil
to the boom actuator 3 together with the first boom control valve
21. By returning the spool 33a to the neutral position, the second
boom control valve 33 can block the communication between the
second hydraulic pump 12 and the boom actuator 3 to stop the flow
of the operating oil to the boom actuator 3. By moving the spool
33a, the second boom control valve 33 can extend the boom actuator
3 (i.e., can lift the boom). By returning the spool 33a to the
neutral position, the second boom control valve 33 can stop the
flow of the operating oil to the boom actuator 3.
The second arm control valve 34 includes a spool 34a and is
connected to the arm actuator 4. By moving the spool 34a, the
second arm control valve 34 connects the second hydraulic pump 12
and the arm actuator 4 to allow the flow of the operating oil to
the arm actuator 4. The second arm control valve 34 changes the
direction of the operating oil flowing to the arm actuator 4
depending on the position of the spool 34a. By moving the spool
34a, the second arm control valve 34 configured as above can extend
or contract the arm actuator 4 (i.e., extend or bend the arm). By
returning the spool 34a to the neutral position, the second arm
control valve 34 configured as above can block the communication
between the second hydraulic pump 12 and the arm actuator 4 to stop
the operation of the arm actuator 4.
The second hydraulic pump 12 is connected to a second center bleed
line 35. The operating oil ejected from the second hydraulic pump
12 is discharged to the tank 24 through the second center bleed
line 35 (bleed-off). The first bucket control valve 32, the second
boom control valve 33, and the second arm control valve 34 are
disposed on the second center bleed line 35 in this order from an
upstream side. An opening area of the second center bleed line 35
changes depending on the positions of the spools 32a to 34a. The
opening area is the largest when the spools 32a to 34a are located
at the neutral positions, and the opening area decreases in
accordance with the amounts of movements of the spools 32a to 34a
from the neutral positions. Therefore, when the spools 32a to 34a
are moved, the opening area of the second center bleed line 35 is
adjusted, and this adjusts the flow rate of the operating oil that
is discharged to the tank 24 through the second center bleed line
35.
A second restrictor 36 is disposed on the second center bleed line
35 so as to be located between the second arm control valve 34 and
the tank 24. A second relief valve 37 is connected to the second
center bleed line 35 so as to avoid the second restrictor 36. In
the second center bleed line 35, hydraulic pressure at an upstream
of the second restrictor 36 increases or decreases by the second
restrictor 36 in accordance with the flow rate of the oil flowing
to the second restrictor 36. When the hydraulic pressure at the
upstream of the second restrictor 36 exceeds predetermined
pressure, the operating oil in the second center bleed line 35 is
relieved to the tank 24 by the second relief valve 37. The
hydraulic pressure increased or decreased by the second restrictor
36 is input as the second negative control pressure Pn2 to the
second regulator 31 together with the ejection pressure Pd2 of the
second hydraulic pump 12.
The second regulator 31 adjusts the tilt angle of the swash plate
12a of the second hydraulic pump 12 in accordance with the second
negative control pressure Pn2, the ejection pressure Pd2, and the
first power shift pressure Ps1 which are input to the second
regulator 31. Since the first power shift pressure Ps1 is
introduced to the second regulator 31, output horsepower of the
second hydraulic pump 12 can be changed together with the first
hydraulic pump 11. On the other hand, output horsepower of the
third hydraulic pump 13 can be controlled independently from the
first hydraulic pump 11 and the second hydraulic pump 12. A turning
control valve 41 and a second bucket control valve 42 are connected
to the third hydraulic pump 13 in parallel. The operating oil
ejected from the third hydraulic pump 13 is introduced to the
turning control valve 41 and the second bucket control valve
42.
The turning control valve 41 includes a spool 41a and is connected
to the turning motor 2. The second bucket control valve 42 includes
a spool 42a and is connected to the bucket actuator 5. By moving
the spool 41a, the turning control valve 41 connects the third
hydraulic pump 13 and the turning motor 2 to allow the flow of the
operating oil to the turning motor 2. The turning control valve 41
changes the direction of the operating oil flowing to the turning
motor 2 depending on the position of the spool 41a. To be specific,
by moving the spool 41a, the turning control valve 41 can rotate
the turning motor 2 clockwise or counterclockwise (i.e., rotate the
turning body clockwise or counterclockwise). By returning the spool
41a to the neutral position, the turning control valve 41 can block
the communication between the third hydraulic pump 13 and the
turning motor 2 to stop the operation of the turning motor 2.
Basically, the second bucket control valve 42 is substantially the
same in configuration as the first bucket control valve 32. By
moving the spool 42a, the second bucket control valve 42 connects
the third hydraulic pump 13 and the bucket actuator 5 to allow the
flow of the operating oil to the bucket actuator 5. The second
bucket control valve 42 changes the direction of the operating oil
flowing to the bucket actuator 5 depending on the position of the
spool 42a. By moving the spool 42a, the second bucket control valve
42 configured as above can extend or contract the bucket actuator 5
(i.e., can cause the bucket to perform excavating or dumping). By
returning the spool 42a to the neutral position, the second bucket
control valve 42 can block the communication between the third
hydraulic pump 13 and the bucket actuator 5 to stop the operation
of the bucket actuator 5.
The third hydraulic pump 13 is connected to a third bleed-off line
43. The operating oil ejected from the third hydraulic pump 13 is
discharged to the tank 24 through the third bleed-off line 43
(bleed-off). The turning control valve 41 and the second bucket
control valve 42 are disposed on the third bleed-off line 43 in
this order from an upstream side. An opening area of the third
bleed-off line 43 changes depending on the positions of the spools
41a and 42a. The opening area is the largest when the spools 41a
and 42a are located at the neutral positions, and the opening area
decreases in accordance with the amounts of movements of the spools
41a and 42a from the neutral positions. Therefore, when the spools
41a and 42a are moved, the opening area of the third bleed-off line
43 is adjusted, and this adjusts the flow rate of the operating oil
that is discharged to the tank 24 through the third bleed-off line
43.
A third restrictor 44 is disposed on the third bleed-off line 43 so
as to be located between the second bucket control valve 42 and the
tank 24. A third relief valve 45 is connected to the third
bleed-off line 43 so as to avoid the third restrictor 44. In the
third bleed-off line 43, hydraulic pressure at an upstream of the
third restrictor 44 increases or decreases by the third restrictor
44 in accordance with the flow rate of the oil flowing to the third
restrictor 44. When the hydraulic pressure at the upstream of the
third restrictor 44 exceeds predetermined pressure, the operating
oil in the third bleed-off line 43 is relieved to the tank 24 by
the third relief valve 45. The hydraulic pressure increased or
decreased by the third restrictor 44 is input as a third negative
control pressure Pn3 to a third regulator 46.
The third regulator 46 adjusts the tilt angle of the swash plate
13a of the third hydraulic pump 13 in accordance with hydraulic
signals input to the third regulator 46. The third negative control
pressure Pn3 and a third ejection pressure Pd3 of the third
hydraulic pump 13 are input as the hydraulic signals to the third
regulator 46. When the third negative control pressure Pn3 or the
third ejection pressure Pd3 increases, the third regulator 46
decreases the tilt angle of the swash plate 13a to reduce the
ejection flow rate of the third hydraulic pump 13. In contrast,
when the third negative control pressure Pn3 or the third ejection
pressure Pd3 decreases, the third regulator 46 increases the tilt
angle of the swash plate 13a to increase the ejection flow rate of
the third hydraulic pump 13. Further, a second power shift pressure
Ps2 is input from a second horsepower controller 47 to the third
regulator 46 configured as above.
The second horsepower controller 47 includes a second
electromagnetic proportional valve 48. Pilot oil is introduced from
the pilot pump 30 to the second horsepower controller 47. The
second electromagnetic proportional valve 48 reduces the pressure
of the pilot oil to the second power shift pressure Ps2
corresponding to a second horsepower control signal input to the
second electromagnetic proportional valve 48. The second
electromagnetic proportional valve 48 outputs the second power
shift pressure Ps2 as the hydraulic signal to the third regulator
46. As with the control with respect to the second negative control
pressure Pn2 and the second ejection pressure Pd2, the third
regulator 46 adjusts the tilt angle of the swash plate 13a in
accordance with the second power shift pressure Ps2 to control the
ejection flow rate of the third hydraulic pump 13. By inputting the
second power shift pressure Ps2 as above, output horsepower of the
third hydraulic pump 13 can be reduced independently from the
output horsepower of the first hydraulic pump 11 and the output
horsepower of the second hydraulic pump 12.
The hydraulic driving system 1 includes a controller 50. The
controller 50 outputs the first horsepower control signal and the
second horsepower control signal to the first horsepower controller
28 and the second horsepower controller 47 in accordance with a
command from a command device (not shown) to control the first
electromagnetic proportional valve 29 and the second
electromagnetic proportional valve 48. With this, the power shift
pressure Ps1 and Ps2 can be output by the controller 50 in
accordance with the command, and the output horsepowers of the
hydraulic pumps 11 to 13 are controlled. By controlling the output
horsepowers as above, the output horsepowers of the first to third
hydraulic pumps 11 to 13 can be controlled without measuring motor
pressure or pump discharge pressure by a hydraulic sensor. Thus,
the hydraulic driving system 1 can be provided at low cost.
As above, the hydraulic driving system 1 includes the three
hydraulic pumps 11 to 13. The control valves 21, 22, 32, 33, 34,
41, and 42 are separately connected to the hydraulic pumps 11 to
13. To be specific, the first boom control valve 21 and the first
arm control valve 22 are connected to the first hydraulic pump 11.
The first bucket control valve 32, the second boom control valve
33, and the second arm control valve 34 are connected to the second
hydraulic pump 12. The turning control valve 41 and the second
bucket control valve 42 are connected to the third hydraulic pump
13. The first bucket control valve 32 and the second bucket control
valve 42 are connected to the hydraulic pumps 12 and 13,
respectively. As shown in FIG. 2, to operate the control valves 21,
22, 32, 33, 34, 41, and 42 connected as above, the hydraulic
driving system 1 includes four operating devices 52 to 55 that are
a boom operating device 52, an arm operating device 53, a bucket
operating device 54, and a turning operating device 55.
These four operating devices 52 to 55 are constituted by operating
valves 52a to 55a, respectively, and the operating valves 52a to
55a include operating levers 52b to 55b, respectively. The
operating valves 52a to 55a are connected to the pilot pump 30. By
operating the operating lever 52b, 53b, 54b, or 55b of the
operating valve 52a, 53a, 54a, or 55a, the operating device 52, 53,
54, or 55 outputs the pilot pressure that has been reduced to
pressure corresponding to an operation amount of the operating
lever 52b, 53b, 54b, or 55b. The output pilot pressure is input to
the control valve 21, 22, 32, 33, 34, 41, or 42, and the control
valve 21, 22, 32, 33, 34, 41, or 42 changes the position of the
spool 21a, 22a, 32a, 33a, 34a, 41a, or 42a in accordance with the
input pilot pressure to allow the flow of the operating oil to the
actuator 2, 3, 4, or 5. Hereinafter, the configurations and
operations of the operating devices 52 to 55 will be explained in
detail in reference to FIGS. 1 and 2.
When the operating lever 52b of the boom operating valve 52a is
operated (a lifting operation or a lowering operation), the boom
operating device 52 outputs one of two pilot pressures XAa and XBa
(boom drive commands) in accordance with an operating direction of
the operating lever 52b. The output pilot pressure XAa or XBa is
input to the first boom control valve 21. The spool 21a of the
first boom control valve 21 moves to a position corresponding to
the input pilot pressure XAa or XBa and allows the flow of the
operating oil to the boom actuator 3 in a direction corresponding
to the input pilot pressure XAa or XBa. With this, the boom is
lowered by the output of the pilot pressure XAa and lifted by the
output of the pilot pressure XBa. The pilot pressure XBa is input
to the second boom control valve 33. The second boom control valve
33 allows the flow of the operating oil to the boom actuator 3 at a
flow rate corresponding to the pilot pressure XBa. Thus, at the
time of the lifting operation, the operating oil is supplied to the
boom actuator 3 through the control valves 21 and 33, and at the
time of the lowering operation, the operating oil is supplied to
the boom actuator 3 through the control valve 21.
When the operating lever 53b of the arm operating valve 53a is
operated (an extending operation or a bending operation), the arm
operating device 53 outputs one of two pilot pressures XAb and XBb
(arm, drive commands) in accordance with the operating direction of
the operating lever 53b. The output pilot pressure XAb or XBb is
input to the first arm control valve 22 and the second arm control
valve 34. The spools 22a and 34a of the first and second arm
control valves 22 and 34 move to positions corresponding to the
input pilot pressure XAb or XBb and allow the flow of the operating
oil to the arm actuator 4 in a direction corresponding to the input
pilot pressure XAb or XBb. To be specific, the operating oil
ejected from the first hydraulic pump 11 and the operating oil
ejected from the second hydraulic pump 12 are supplied to the arm
actuator 4 through the control valves 22 and 34. With this, the arm
is extended by the output of the pilot pressure XAb and is bent by
the output of the pilot pressure XBb from the boom operating device
52.
When the operating lever 55b of the turning operating valve 55a is
operated (a clockwise operation or a counterclockwise operation),
the turning operating device 55 outputs one of two pilot pressures
XAs and XBs (turn commands) in accordance with the operating
direction of the operating lever 55b. The output pilot pressure XAs
or XBs is input to the turning control valve 41. The spool 41a of
the turning control valve 41 moves to a position corresponding to
the input pilot pressure XAs or XBs and allows the flow of the
operating oil to the turning motor 2 in a direction corresponding
to the input pilot pressure XAs or XBs. With this, the turning body
is turned clockwise by the output of the pilot pressure XAs and
turned counterclockwise by the output of the pilot pressure XBs.
Further, the turning operating device 55 includes a selective valve
56. When the turning operating device 55 outputs the pilot pressure
XAs or XBs, the selective valve 56 outputs a pilot pressure
XCs.
When the operating lever 54b (operating lever) of the bucket
operating valve 54a is operated (a dumping operation or an
excavating operation), the bucket operating device 54 outputs one
of two pilot pressures XAk0 and XBk0 (bucket drive commands) in
accordance with the operating direction of the operating lever 54b.
The bucket operating device 54 further includes a direction
switching valve 57. The pilot pressure XAk0 or XBk0 output from the
bucket operating valve 54a is input to the direction switching
valve 57. The direction switching valve 57 is a switching valve
configured to switch a destination to which the pilot pressure XAk0
or XBk0 is output, in accordance with whether or not the operating
lever 55a of the turning operating device 55 is operated. The
direction switching valve 57 includes a spool 57a. The spool 57a
moves between a first position S1 and a second position S2 in
accordance with whether or not the pilot pressure XCs is input.
When the pilot pressure XCs is output from the selective valve 56,
the spool 57a moves to the first position S1. When the pilot
pressure XCs is not output, the spool 57a returns to the second
position S2. At the first position S, the input pilot pressure XAk0
or XBk0 is output as a pilot pressure XAk1 or XBk1 (first bucket
drive command). At the second position S2, the input pilot pressure
XAk0 or XBk0 is output as a pilot pressure XAk2 or XBk2 (second
bucket drive command).
The pilot pressure XAk1 or XBk1 is input to the first bucket
control valve 32, and the spool 32a moves to a position
corresponding to the input pilot pressure XAk1 or XBk1. With this,
the operating oil ejected from the second hydraulic pump 12 flows
to the bucket actuator 5 in a direction corresponding to the input
pilot pressure XAk1 or XBk1. To be specific, the bucket performs
dumping by the output of the pilot pressure XAk1 and performs
excavating by the output of the pilot pressure XBk1. At this time,
the first bucket control valve 32 connects the second hydraulic
pump 12 and the bucket actuator 5 by an opening area corresponding
to the input pilot pressure XAk1 or XBk1, so that the bucket
actuator 5 can be extended or contracted at an
extension/contraction speed corresponding to the operation amount
of the operating lever 54b of the bucket operating valve 54a.
On the other hand, the pilot pressure XAk2 or XBk2 is input to the
second bucket control valve 42, and the spool 42a moves to a
position corresponding to the input pilot pressure XAk2 or XBk2.
With this, the operating oil ejected from the third hydraulic pump
13 flows to the bucket actuator 5 in a direction corresponding to
the input pilot pressure XAk2 or XBk2. To be specific, the bucket
performs dumping by the output of the pilot pressure XAk2 and
performs excavating by the output of the pilot pressure XBk2. At
this time, the second bucket control valve 42 connects the third
hydraulic pump 13 and the bucket actuator 5 by an opening area
corresponding to the input pilot pressure XAk2 or XBk2, so that the
bucket actuator 5 can be extended or contracted at a speed
corresponding to the operation amount of the operating lever 54b of
the bucket operating valve 54a.
In the hydraulic driving system 1 configured as above, the first
boom control valve 21, the first arm control valve 22, the second
boom control valve 33, and the second arm control valve 34 are
connected to the first hydraulic pump 11 and the second hydraulic
pump 12. The turning control valve 41 and the second bucket control
valve 42 other than the first boom control valve 21, the first arm
control valve 22, the first bucket control valve 32, the second
boom control valve 33, and the second arm control valve 34 are
connected to the third hydraulic pump 13. Therefore, when the
operating lever 52a of the boom operating device 52 and the
operating lever 53a of the arm operating device 53 are operated,
the operating oil is supplied from the first hydraulic pump 11 and
the second hydraulic pump 12 to the boom actuator 3 and the arm
actuator 4. On this account, even when the operating levers 52a and
53a and the operating lever 55b of the turning operating device 55
are operated at the same time, the operating oil ejected from the
third hydraulic pump 13 is not supplied to the boom actuator 3 or
the arm actuator 4. Further, regardless of the presence or absence
of the pilot pressure XAs or XBs, a pressure liquid can be supplied
from the first hydraulic pump 11 and the second hydraulic pump 12
to the boom actuator 3 or the arm actuator 4 at a required flow
rate.
Since the operating oil ejected from the third hydraulic pump 13 is
not supplied to the boom actuator 3 or the arm actuator 4 as above,
the third hydraulic pump 13 can be used as a hydraulic pump only
for driving the turning motor 2. Therefore, for the purpose of
supplying the operating oil from the hydraulic pump preferentially
to the turning motor 2, it is unnecessary to restrict the flow rate
of the operating oil flowing to the other control valve. On this
account, energy loss can be reduced, and energy saving at the time
of the turning operation can be achieved. Further, since the third
hydraulic pump 13 is a hydraulic pump only for the turning motor 2,
the third hydraulic pump 13 is only required to eject the operation
oil at a required flow rate corresponding to the operation of the
operating lever 55b of the turning operating device 55. Thus, the
energy saving at the time of the turning operation can be further
achieved.
In the hydraulic driving system 1, the second bucket control valve
42 is connected to the third hydraulic pump 13, and in addition,
the first bucket control valve 32 that drives the bucket actuator 5
is connected to the second hydraulic pump 12. When the operating
lever 54b of the bucket operating device 54 is operated while the
operating lever 55b of the turning operating device 55 is not
operated, the direction switching valve 57 outputs the pilot
pressure XAk1 or XBk1 to the second bucket control valve 42 to
drive the bucket actuator 5 by the third hydraulic pump 13. On the
other hand, when the operating lever 55b of the turning operating
device 55 is operated at the same time as the operating lever 54b
of the bucket operating device 54, the direction switching valve 57
of the bucket operating device 54 outputs the pilot pressure XAk2
or XBk2 to the first bucket control valve 32 to drive the bucket
actuator 5 by the second hydraulic pump 12. To be specific, the
bucket actuator 5 is driven in accordance with the presence or
absence of the pilot pressure XCs, and the operating oil ejected
from the third hydraulic pump 13 is not supplied to the bucket
actuator 5 at the time of the turning operation. Therefore, even
when the turning operating device 55 and the bucket operating
device 54 are operated at the same time, the third hydraulic pump
13 can be used as a hydraulic pump only for driving the turning
motor 2. Further, by selectively using one of the first bucket
control valve 32 and the second bucket control valve 42 in
accordance with the presence or absence of the pilot pressure XCs,
the pressure liquid can be supplied to the bucket actuator 5 at a
required flow rate regardless of whether or not the turning
operation is performed (i.e., regardless of whether or not the
operating oil is supplied to the turning motor 2).
As above, in the hydraulic driving system 1, the pressure liquid
can be supplied to the boom actuator 3, the arm actuator 4, or the
bucket actuator 5 at a required flow rate regardless of whether or
not the turning operation is performed. Therefore, even when the
boom, the arm, or the bucket is operated at the same time as the
turning operation, the pressure liquid can be supplied to each
actuator at a required flow rate.
Further, when the operating lever 52b of the boom operating device
52, the operating lever 53b of the arm operating device 53, or the
operating lever 54b of the bucket operating device 54 is operated
at the same time as the operating lever 55b of the turning
operating device 55, the operating oil can be supplied to the
actuators 3 to 5 from the hydraulic pumps 11 and 12 other than the
third hydraulic pump 13. To be specific, the hydraulic pumps 11 to
13 are only required to eject the operating oil at a flow rate
required for driving each of the actuators 2 to 5. Therefore, the
operating oil can be prevented from being ejected wastefully from
the hydraulic pumps 11 to 13.
In the hydraulic driving system 1, the first bucket control valve
32 and the second bucket control valve 42 are substantially the
same in configuration as each other, and the opening area of the
control valve 32 with respect to the input pilot pressure and the
opening area of the control valve 42 with respect to the input
pilot pressure are substantially the same as each other. Therefore,
the flow rate of the operating oil flowing to the bucket actuator 3
from the first bucket control valve 32 with respect to the
operation amount of the operating lever 54b of the bucket operating
device 54 and the flow rate of the operating oil flowing to the
bucket actuator 3 from the second bucket control valve 42 with
respect to the operation amount of the operating lever 54b of the
bucket operating device 54 are substantially the same as each
other. If the pilot pressures XAk1 and XAk2 are substantially the
same as each other, or the pilot pressures XBk1 and XBk2 are
substantially the same as each other, the extension/contraction
speeds of the bucket actuator 5 with respect to these pilot
pressures can be made substantially the same as each other.
Therefore, regardless of whether or not the turning operation is
performed, the bucket actuator 5 can be driven at the
extension/contraction speed corresponding to the operation amount
of the operating lever 54b of the bucket operating device 54. Thus,
regardless of whether or not the turning operation is performed at
the same time, the bucket can be operated by the same operational
feeling.
In the hydraulic driving system 1, the first bucket control valve
32 is connected to the second hydraulic pump 12 to which the second
boom control valve 33 is connected. Only when the pilot pressure
XBa is output from the boom operating device 52, that is, only when
the lifting operation of the boom is performed, the second boom
control valve 33 supplies the operating oil to the boom actuator 3.
To be specific, when the lowering operation of the boom is
performed, the second boom control valve 33 does not supply the
operating oil to the boom actuator 3. Therefore, when the bucket is
operated at the same time as the lowering operation of the boom,
the operating oil can be supplied from the second hydraulic pump 12
through the first bucket control valve 32 to the bucket actuator 5
at a required flow rate.
Embodiment 2
A hydraulic driving system 1A of Embodiment 2 is similar in
configuration to the hydraulic driving system 1 of Embodiment 1.
Therefore, regarding the hydraulic driving system 1A, only
components different from the components of the hydraulic driving
system 1 of Embodiment 1 will be explained, and explanations of the
same components are omitted. The same is true for a hydraulic
driving system 1B of Embodiment 3 described below.
In the hydraulic driving system 1A of Embodiment 2, a first bucket
control valve 32A includes a movement regulating mechanism 39. When
the excavating operation of the bucket is performed while the boom
or the arm is operated, the movement regulating mechanism 39
regulates the amount of movement of the spool 32a of the first
bucket control valve 32A to regulate the flow rate of the operating
oil flowing to the bucket actuator 5. The configuration of the
movement regulating mechanism 39 will be explained in detail. The
movement regulating mechanism 39 is constituted by, for example, a
piston 39a. The piston 39a receives as a pilot pressure PCK a
highest pressure among the pilot pressures output from the boom
operating valve 52a and the arm operating valve 53a. The piston 39a
moves toward the spool 32a by the pilot pressure PCK. With this,
the movement of the spool 32a is regulated, and therefore, the flow
rate of the operating oil supplied to the bucket actuator 5 at the
time of the excavating operation of the bucket (i.e., at the time
of the extending operation of the bucket actuator 5) is regulated.
With this, when the turning body is turned, and the boom or the arm
is operated at the same time as the bucket, the operating oil can
be supplied to the boom actuator 3 or the arm actuator 4 at a
required flow rate.
The hydraulic driving system 1A has the same operational advantages
as the hydraulic driving system 1 of Embodiment 1.
Embodiment 3
In an hydraulic driving system 1B of Embodiment 3, a first bucket
electromagnetic valve 61 and a second bucket electromagnetic valve
62 are provided at the first bucket control valve 32, and a third
bucket electromagnetic valve 63 and a fourth bucket electromagnetic
valve 64 are provided at the second bucket control valve 42. These
four bucket electromagnetic valves 61 to 64 constitute a command
output device 60 together with a controller 50B and are connected
to the pilot pump 30. Each of the bucket electromagnetic valves 61
to 64 outputs the pilot pressure corresponding to a signal input
from the controller 50B. The first bucket electromagnetic valve 61
outputs the pilot pressure XAk1 to the first bucket control valve
32, and the second bucket electromagnetic valve 62 outputs the
pilot pressure XBk1 to the first bucket control valve 32. The third
bucket electromagnetic valve 63 outputs the pilot pressure XAk2 to
the second bucket control valve 42, and the fourth bucket
electromagnetic valve 64 outputs the pilot pressure XBk2 to the
second bucket control valve 42.
A first sensor PS1 and a second sensor PS2 are provided at the
bucket operating device 54, and a third sensor PS3 is provided at
the turning operating device 55. The first sensor PS1 detects the
pilot pressure XAk0 output from the bucket operating valve 54a, and
the second sensor PS2 detects the pilot pressure XBk0 output from
the bucket operating valve 54a. The third sensor PS3 detects the
pilot pressure XCs output from the selective valve 56. The first to
third sensors PS1 to PS3 are electrically connected to the
controller 50B.
The controller 50B outputs first to fourth bucket drive signals in
accordance with detection results from the first to third sensors
PS1 to PS3. Specifically, when the third sensor PS3 detects the
pilot pressure XCs, and the first sensor PS detects the pilot
pressure XAk0, the controller 50B outputs the first bucket drive
signal corresponding to the pilot pressure XAk0 to the first bucket
electromagnetic valve 61. When the third sensor PS3 detects the
pilot pressure XCs, and the second sensor PS2 detects the pilot
pressure XBk0, the controller 50B outputs the second bucket drive
signal corresponding to the pilot pressure XBk0 to the second
bucket electromagnetic valve 62. When the third sensor PS3 does not
detect the pilot pressure XCs, and the first sensor PS1 detects the
pilot pressure XAk0, the controller 50B outputs the third bucket
drive signal corresponding to the pilot pressure XAk0 to the third
bucket electromagnetic valve 63. When the third sensor PS3 does not
detect the pilot pressure XCs, and the second sensor PS2 detects
the pilot pressure XBk0, the controller 50B outputs the fourth
bucket drive signal corresponding to the pilot pressure XBk0 to the
fourth bucket electromagnetic valve 64.
According to the hydraulic driving system 1B configured as above,
as with the hydraulic driving system 1 of Embodiment 1, when the
operating lever 55b of the turning operating device 55 is operated,
the third hydraulic pump 13 can be used as a hydraulic pump only
for driving the turning motor 2 regardless of whether or not the
other operating devices 52 to 54 are operated.
In the hydraulic driving system 1B, a boom electromagnetic valve 71
is provided at the second boom control valve 33, and a first arm
electromagnetic valve 72 and a second arm electromagnetic valve 73
are provided at the first arm control valve 22. The boom
electromagnetic valve 71 and the two arm electromagnetic valves 72
and 73 are connected to the pilot pump 30, and the operations
thereof are controlled by the controller 50B. To be specific, the
boom electromagnetic valve 71 outputs the pilot pressure XBa2
corresponding to the signal input from the controller 50B, and the
two arm electromagnetic valves 72 and 73 output the pilot pressures
XAb2 and XBb2 corresponding to the signals input from the
controller 50B.
A fourth sensor PS4 and a fifth sensor PS5 are provided at the boom
operating device 52, and a sixth sensor PS6 and a seventh sensor
PS7 are provided at the arm operating device 53. The fourth sensor
PS4 detects the pilot pressure XAa output from the boom operating
valve 52a, and the fifth sensor PS5 detects the pilot pressure XBa
output from the boom operating valve 52a. The sixth sensor PS3
detects the pilot pressure XAb output from the arm operating valve
53a, and the seventh sensor PS7 detects the pilot pressure XBb
output from the arm operating valve 53a. The fourth to seventh
sensors PS4 to PS7 are electrically connected to the controller
50B.
The controller 50B outputs a boom drive signal and first and second
arm drive signals in accordance with detection results from the
fourth to seventh sensors PS4 to PS7. Specifically, when the fifth
sensor PS5 detects the pilot pressure XBa, the controller 50B
outputs the boom drive signal corresponding to the pilot pressure
XBa to the boom electromagnetic valve 71. When the sixth sensor PS6
detects the pilot pressure XAb, the controller 50B outputs the
first arm drive signal corresponding to the pilot pressure XAb to
the first arm electromagnetic valve 72. When the seventh sensor PS7
detects the pilot pressure XBb, the controller 50B outputs the
second arm drive signal corresponding to the pilot pressure XBb to
the second arm electromagnetic valve 73.
In the hydraulic driving system 1B configured as above, when the
operating lever 52b of the boom operating device 52 is operated,
the boom operating device 52 outputs the pilot pressure XBa, and
the pilot pressure XBa is input to the first boom control valve 21.
When the fifth sensor PS5 detects the pilot pressure XBa, the
controller 50B outputs the boom drive signal corresponding to the
output pilot pressure XBa to the boom electromagnetic valve 71. The
boom electromagnetic valve 71 inputs the pilot pressure XBa2
corresponding to the first boom drive signal to the second boom
control valve 33. With this, when the operating lever 52b of the
boom operating device 52 is operated as above, the operating oil
can be supplied from the two hydraulic pumps 11 and 12 through the
first boom control valve 21 and the second boom control valve 33 to
the boom actuator 3, and the boom can be lifted by the two
hydraulic pumps 11 and 12.
Similarly, when the operating lever 53b of the arm operating device
53 is operated, the arm operating device 53 outputs, for example,
the pilot pressure XAb, and the pilot pressure XAb is input to the
second arm control valve 34. When the sixth sensor PS6 detects the
pilot pressure XAb, the controller 50B13 outputs the first arm
drive signal corresponding to the pilot pressure XAb to the first
arm electromagnetic valve 72. The first arm electromagnetic valve
72 inputs the pilot pressure XAb2 corresponding to the first arm
drive signal to the first arm control valve 22. With this, when the
operating lever 53b of the arm operating device 53 is operated as
above, the operating oil can be supplied from the two hydraulic
pumps 11 and 12 through the first arm control valve 22 and the
second arm control valve 34 to the arm actuator 4, and the arm can
be bent or extended by the two hydraulic pumps 11 and 12.
In the hydraulic driving system 1B configured as above, to perform,
for example, a bucket horizontally pulling operation (the lifting
operation of the boom and the bending operation of the arm), the
operating lever 52b of the boom operating device 52 and the
operating lever 53b of the arm operating device 53 may be operated
at the same time. In this case, when the controller 50B detects the
pilot pressures XBa and XAb based on the detection results from the
fifth sensor PS5 and the sixth sensor PS6, the controller 50B
drives the boom actuator 3 only by the first hydraulic pump 11 and
drives the arm actuator 4 only by the second hydraulic pump 12
without outputting the boom drive signal and the first arm signal.
As above, in the hydraulic driving system 1B, by controlling the
operations of the boom electromagnetic valve 71 and the first arm
electromagnetic valve 72, the boom actuator 3 and the arm actuator
4 can be driven by the hydraulic pumps 11 and 12, respectively.
With this, the operating oil supplied to the boom actuator 3 and
the operating oil supplied to the arm actuator 4 can be controlled
individually, and therefore, the flow rate of the operating oil can
be distributed to the actuators 4 and 5 without waste. Thus, the
energy saving of the hydraulic driving system 1B can be
achieved.
Further, in the hydraulic driving system 1B, the operating lever
54b of the bucket operating valve 54a may be operated at the same
time as the operating lever 52b of the boom operating device 52 and
the operating lever 53b of the arm operating device 53. In this
case, the controller 50B controls the operation of the third or
fourth bucket electromagnetic valve 63 or 64 in accordance with the
operating direction of the operating lever 54b and inputs the pilot
pressure XAk2 or XBk2 to the second bucket control valve 42. With
this, the operating oil is supplied from the third hydraulic pump
13 through the second bucket control valve 42 to the bucket
actuator 5. Therefore, the operating oil supplied to the bucket
actuator 5 can be controlled separately from the operating oil
supplied to the boom actuator 3 and the operating oil supplied to
the arm actuator 4, and therefore, the flow rate of the operating
oil can be distributed to the actuators 3 to 5 without waste. Thus,
the energy saving of the hydraulic driving system 1B can be
achieved.
Furthermore, when the operating lever 52b of the boom operating
device 52 or the operating lever 53b of the arm operating device 53
is operated at the same time as the operating lever 55b of the
turning operating device 55 and the operating lever 54b of the
bucket operating device 54, such as when the turning operation of
the turning body, the excavating operation of the bucket, and the
lifting operation of the boom are performed at the same time, the
controller 50B detects three simultaneous operations based on the
detection results from the second sensor PS2, the third sensor PS3,
and the fifth sensor PS5. When the controller 50B detects the three
simultaneous operations, it outputs the boom drive signal to the
boom electromagnetic valve 71 and also outputs the second bucket
drive signal to the second bucket electromagnetic valve 62. At this
time, the controller 50B limits the second bucket drive signal (for
example, outputs a signal obtained by multiplying the second bucket
drive signal (current) at the time of a single operation by a
correction coefficient of less than one) to limit the pilot
pressure XBk1 output from the second bucket electromagnetic valve
62. Thus, the amount of movement of the spool 32a of the first
bucket control valve 32A is regulated, and as a result, the flow
rate of the operating oil flowing to the bucket actuator 5 is
regulated. With this, when the turning body is turned, and the boom
and the bucket are operated at the same time, the operating oil can
be supplied to the boom actuator 3 at a required flow rate,
Other Embodiments
In each of the hydraulic driving systems 1, 1A, and 1B of
Embodiments 1 to 3, the first bucket control valve 32 is connected
to the second hydraulic pump 12. However, the first bucket control
valve 32 may be connected to the first hydraulic pump 11. Further,
each of the order of the control valves 21 and 22 disposed on the
first center bleed line 23 and the order of the control valves 32,
33, and 34 disposed on the second center bleed line 35 is not
limited to the above order and may be any order. Furthermore, the
first arm control valve 22 and the second boom control valve 33 are
not necessarily required, and one or both of those may not be
included.
As in each of the hydraulic driving systems 1, 1A, and 1B of
Embodiments 1 to 3, it is preferable that only the turning control
valve 41 and the second bucket control valve 42 be connected to the
third hydraulic pump 13. However, valves other than control valves,
such as the first boom control valve 21, the first arm control
valve 22, the second boom control valve 33, and the second arm
control valve 34, through which the operating oil is supplied to
the actuators 3 and 4 at a high flow rate may be connected to the
third hydraulic pump 13. For example, a control valve, such as an
auxiliary control valve or a control valve for driving a dozer,
through which the operating oil is supplied to the actuator at a
relatively low flow rate may be connected to the third hydraulic
pump 13.
Each of the hydraulic driving systems 1, 1B, and 1A of Embodiments
1 to 3 may be configured to perform hydraulic drive of a traveling
device. In this case, since the flow rate of the operating oil
supplied to the traveling motor is high, a control valve through
which the operating oil is supplied to a traveling motor of the
traveling device is connected to the hydraulic pumps other than the
third hydraulic pump 13, that is, to the first hydraulic pump 11
and the second hydraulic pump 12 as with the first boom control
valve 21, the first arm control valve 22, the second boom control
valve 33, and the second arm control valve 34.
In each of the hydraulic driving systems 1, 1A, and 1B, a plurality
of control valves are connected to the first to third hydraulic
pumps 11 to 13 in parallel. However, the control valves may be
directly connected, and a method of connecting the control valves
is not limited.
In each of the hydraulic driving systems 1, 1A, and 1B, the
operating oil is used as the pressure liquid. However, the pressure
liquid is not limited to the operating oil and may be water, other
liquid, or the like. Further, each of the hydraulic driving systems
1, 1A, and 11B is applied to the hydraulic excavator. However, a
construction machine to which each of the hydraulic driving systems
1, 1A, and 1B is applied is not limited to the hydraulic excavator
and may be a crane, a dozer, or the like,
From the foregoing explanation, many modifications and other
embodiments of the present invention are obvious to one skilled in
the art. Therefore, the foregoing explanation should be interpreted
only as an example and is provided for the purpose of teaching the
best mode for carrying out the present invention to one skilled in
the art. The structures and/or functional details may be
substantially modified within the scope of the present
invention.
REFERENCE SIGNS LIST
1, 1A, 1B hydraulic driving system
2 turning motor
3 boom actuator
4 arm actuator
5 bucket actuator
11 first hydraulic pump
12 second hydraulic pump
13 third hydraulic pump
21 first boom control valve
22 first arm control valve
32, 32A first bucket control valve
33 second boom control valve
34 second arm control valve
39 movement regulating mechanism
41 turning control valve
42 second bucket control valve
50 controller
50B controller
52 boom operating device
52b operating lever
53 arm operating device
53b operating lever
54 bucket operating device
54b operating lever
55 turning operating device
55b operating lever
60 command switching device
61 first bucket electromagnetic valve
62 second bucket electromagnetic valve
63 third bucket electromagnetic valve
64 fourth bucket electromagnetic valve
71 boom electromagnetic valve
72 first arm electromagnetic valve
73 second arm electromagnetic valve
* * * * *